[Request]: Relinquish freed filesystem blocks back to macOS.

[jglogan]

Feature or enhancement request details

container root filesystems and named volumes use AFPS files containing sparse ext4 disk images.

If a container runs long enough and unlinks files along the way, more and more of the sparse image will show as in use on the host, even for fs blocks that are free after previously having been used.

Virtualization Framework will recover blocks that the guest trims using the FSTRIM ioctl

We should:

• Determine the UX for cleaning up containers and volumes. For this issue we should start simple and build from there.
  • It can be done automatically, on a schedule, or user-directed. [Request]: vminit API for block device operations, initially for freeze/thaw. containerization#660 would provide the mechanism for the operation.
  • It could apply to all block device mounts for a container, or specific ones (this seems fussy).

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